1. Field of the Invention
The present invention relates to a top mold of an injection molding machine, provided with a heating wire extending from an external power source to the injection nozzles of the top mold through a heating wire guide hole while passing around the manifold and electrically heating the injection nozzles during an injection molding process, and, more particularly, to a structural improvement in such a top mold allowing easy and simple repair or replacement of the heating wire within a short period of time without entirely disassembling the top mold, the structural improvement thus reducing the maintenance cost of the top mold and reducing the time the injection molding process Us stopped while repairing or replacing the heating wire.
2. Description of the Prior Art
In an injection molding process of producing plastic products, a molten plastic material is contained in an injection cylinder provided at a side of an injection molding machine, and is injected into the cavity formed in a bottom mold. In order to smoothly and uniformly inject the molten plastic material into the cavity of the bottom mold, a manifold is formed in the top mold, with a plurality of injection nozzles provided in the top mold at positions under the manifold for injecting the molten plastic material into the cavity of the bottom mold. During an injection molding process, a molten plastic material under pressure is injected into the cavity of the mold. When the plastic material within the cavity is hardened, the top mold is separated from the bottom mold so as to remove the plastic product from the cavity.
In order to prevent the molten plastic material from being undesirably hardened when it flows from the injection cylinder into the cavity of the bottom mold, a heating wire is arranged around both the manifold and the injection nozzles. That is, the heating wire passes through the manifold to heat the manifold, thus preventing the molten plastic material from being undesirably hardened within the manifold. The heating wire is also wound around the injection nozzles, and heats the nozzles. It is thus possible for the conventional top mold of the injection molding machine to prevent the molten plastic material from being undesirably hardened when the plastic material flows in the manifold or the injection nozzles during an injection molding process.
FIG. 1 is a sectional view of a conventional top mold of an injection molding machine. As shown in the drawing, the conventional top mold 1 of an injection molding machine includes a pouring gate 2, which is formed in a cylinder housing 3 such that the gate 2 communicates with an injection cylinder (not shown). The pouring gate 2 also communicates with a manifold 4, and guides molten plastic material from the injection cylinder into the cavity of the mold through the manifold 4. This manifold 4 is formed in the manifold housing 5 provided at a position under the cylinder housing 3.
A plurality of injection nozzles 8 are formed in the top mold at positions under the manifold 4. The injection nozzles 8 are held in their places by a nozzle housing 7. A heating wire guide hole 6 is formed along the junction of the cylinder housing 3 and the manifold housing 5, with a heating wire 9 extending from an external power source (not shown) to the injection nozzles 8 through the guide hole 6 while passing around the manifold 4. The heating wire 9 is wound around the injection nozzles 8, and electrically heats the injection nozzles 8, in addition to heating the manifold 4.
When the heating wire 9 is electrically activated, it heats both the manifold 4 and the injection nozzles 8. Therefore, the molten plastic material flowing from the pouring gate 2 to the cavity of a bottom mold through both the manifold 4 and the injection nozzles 8 retains its molten phase by the heating wire 9, which passes around the manifold 4 and is wound around the injection nozzles 8.
However, the top mold 1 having such a conventional heating wire arrangement is problematic in that it is very difficult to repair or replace the heating wire 9. That is, when the heating wire 9 is undesirably cut, it is necessary to repair the wire 9 or replace the wire 9 with a new one. In such a case, the entire structure of the conventional top mold 1 must be disassembled since the heating wire 9 is led into the mold 1 through the heating wire guide hole 8 formed along the junction of the cylinder housing 3 and the manifold housing 5.
Therefore, the top mold 1 having such a heating wire arrangement is inconvenient to users and excessively consumes time while repairing the heating wire 9 or replacing the wire 9 with a new one. The top mold 1 also increases its maintenance cost. Since the injection molding process must be stopped for an undesired lengthy period of time during the process of repairing or replacing the heating wire, the productivity of the molded products is reduced.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a top mold of an injection molding machine, which is designed to allow easy and simple repair or replacement of a heating wire within a short period of time without entirely disassembling the top mold, and which is thus reduced in its maintenance cost and reduces the time the injection molding process is stopped while repairing or replacing the heating wire.
In order to accomplish the above object, the present invention provides a top mold of an injection molding machine, comprising a cylinder housing having a pouring gate, a manifold housing having a manifold and mounted on the lower surface of the cylinder housing, a nozzle housing having an injection nozzle and mounted on the lower surface of the manifold housing, and a heating wire wound around the injection nozzle, further comprising: a power supply wire guide hole formed on the lower surface of the nozzle housing; a power supply wire extending from an external power source to the heating wire through the power supply wire guide hole; a clip holding slit formed on the sidewall of the power supply wire guide hole; and a clip held in the clip holding slit and supporting the power supply wire at a desired place within the power supply wire guide hole; a connector connecting the power supply wire to the heating wire.